1. Field of the Invention
The invention is directed to a method and apparatus for installing contacts into a mounting member such as an apertured substrate or a connector insulator body; more particularly, to a novel method and apparatus for pull-fitting press fittable contacts into apertures in a mounting member.
2. History of the Prior Art
In the recent past, press-fit technology has provided marked improvements in the manner in which contacts are rigidly mounted in substrates and other mounting fixtures and has, thus, virtually revolutionized the manufacturing techniques utilized in the electrical interconnection industry.
Prior to press fitting contacts into apertures formed in printed circuit board substrates, electrical terminals were conventionally soldered therein. Solder comprising a tin/lead alloy has been, and to a certain extent still is, a metallurgical mainstay of the electrical connector industry. Certain innovations have, however, proposed means for replacing solder and the problems associated therewith in the connector industry. U.S. Pat. No. 4,216,576, assigned to the assignee of the present invention, teaches such technology which includes coating insulative substrates and plated through apertures therein with a protective resin coating which is selectively penetrated during the process of press fitting the contact into position. It may be seen, however, that in general only those contacts and contact-insulator configurations which lend themselves to receiving and transferring press fit forces may be utilized with the "solderless" electrical connector technology. It is advantageous to provide manufacturing methods and apparatus whereby connectors of all designs may reap the benefits of a press fit and/or solderless interconnection with a plated through hole with which it is electrically and mechanically interconnected.
Traditionally, press-fit technology has required a contact which includes a transversely broadened press-fit bullet region which is to be received with an interference fit into a plated through aperture in a printed circuit board or into an aperture in a connector insulator. A pair of transversely extending shoulders immediately above the press-fit region are generally provided and used to transmit press fitting forces from the installation tool to the contacts so as to produce a reliable electrical and mechanical interengagement between the contact and an aperture after it has been interference fitted into position. The broad concept of press fit technology is shown and described in U.S. Pat. No. 3,671,917 assigned to the assignee of the present invention.
In certain connector applications and with certain types of electrical contacts it is impossible to provide a press fit load transmitting shoulder. For example, where a press fit region is provided on a contact formed from either square wire stock or formed by means of a screw machine into a cylindrical type of contact, it is not generally possible to form a press insertion load bearing shoulder upon the contacts. The manufacture of such contacts and a further discussion of the problems is set forth and described in copending U.S. patent application Ser. No. 174,889, assigned to the assignee of the present invention. In summary, it is necessary in such contact embodiments to provide other means for applying a longitudinal force of sufficient magnitude to the contacts in order to press fit them into receiving apertures.
Certain prior art metal-to-metal connector constructions have approached press fit assembly problems by providing an upper contact mating region comprising a narrow blade portion which also defines a lower, press fit shoulder. One such contact, formed from square wire stock, is shown and described in U.S. Pat. No. 4,035,047 assigned to the assignee of the present invention. However, card edge connector contacts formed from square wire generally include a bowed or folded bellows type mating region which essentially prohibits the application of a press fitting force directly to the top of the contact and utilizes the required transversely extending press fit insertion load bearing shoulder region to seat the contact. For this reason many card edge connectors may be rigidly mounted only by wave soldering of the contacts into plated through holes in a mounting substrate.
Prior art pull fitting machines have been used to pull contacts into an insulator but these have required more complex construction, not adapted to different contact spacings. Moreover, none of these prior art devices could pull contacts into a wide mounting substrate such as a printed circuit board.
Many contact-insulator assemblies constructed today without press fit contact regions comprise what is generally called a discrete connector. This assembly is usually mounted to an insulative substrate such as FR-4 or G-10 printed circuit board material by soldering of the contact tails within plated apertures through the substrate. Since most discrete connectors are not constructed in a manner facilitating press fit or the advantages thereof, it would be of enormous advantage to provide a means for affecting a press fit interconnection with existing discrete connector designs. The initial problem in applying press fit technology to the mounting of a discrete connector is the provision of a transversely extending press fit bullet region on the discrete connector contact tail. This aspect is addressed in copending U.S. patent application Ser. No. 174,889, assigned to the assignee of the present invention. The method and apparatus for coining a press fit bullet portion on such contacts thus permits a manner of press fit assembly which is not limited in approach by the individual connector configuration. For example, a contact having a fragile bellows-type contacting region, as shown in said copending application, cannot be press fitted by the application of a top loaded insertion force. The method and apparatus of the present invention provide a means for "pull fitting" electrical contacts into apertures located in a substrate or other receiving member. In this manner any contact configuration can incorporate the multitudinous advantages of press fit technology for solderless interconnection.